# Calculating the gravitational acceleration

When calculating the gravitational acceleration between two objects of comparable mass, should I find the acceleration caused by gravity for both masses and then add the accelerations togeether, or should I just find the acceleration for one of the masses? I was thinking that since there's a gravitational force acting on both objects, I should find the accelerations caused by gravity for both objects before getting the acceleration of the objects towards each other.

When calculating the gravitational acceleration between two objects of comparable mass … I was thinking that since there's a gravitational force acting on both objects, I should find the accelerations caused by gravity for both objects before getting the acceleration of the objects towards each other.

Hi wrongusername! Yes. The essential principle is that (unless you're working in general relativity, which I'm assuming you're not) F = ma etc only works in an inertial frame.

So you can't calculate on the basis that one body is fixed (unless of course it's sooo much heavier than the other, eg the Earth and you, that it's as good as fixed).

Calculate each acceleration from the point of view of a fixed observer, and proceed from there. Hi wrongusername! Yes. The essential principle is that (unless you're working in general relativity, which I'm assuming you're not) F = ma etc only works in an inertial frame.

So you can't calculate on the basis that one body is fixed (unless of course it's sooo much heavier than the other, eg the Earth and you, that it's as good as fixed).

Calculate each acceleration from the point of view of a fixed observer, and proceed from there. Thank you for the explanation! 